This application claims the priority of Korean Patent Application No. 2001-65484, filed Oct. 23, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method for detecting the binding of biomolecules, and more particularly, to a method and sensor for detecting the binding of probes and target biomolecules on a bio-chip by measuring the shear stress on a sensor substrate, to which the biomolecules are bound, before and after binding of the target molecules to the probes.
2. Description of the Related Art
Bio-chips, which are constructed by attaching a number of DNA or protein probes having a complementary sequence that can bind to target molecules of interest on a substrate at a high density, are used for analyzing a gene expression pattern, deficiency, protein distribution, or reaction pattern in the target sample. Bio-chips can be classified into micro-array chips with probes immobilized on a solid surface and labs-on-a-chip with probes immobilized on micro-channels according to the way probes are attached. Bio-chips also can be classified into DNA-chips, protein-chips, etc., according to the kind of the probes. Those bio-chips need a system for detecting the binding of biomolecules in a sample to the probes immobilized on a substrate in order to identify whether a target biomolecule of interest exists in the sample.
Most currently available DNA chips for gene array fluorescently detect target molecules in a sample. U.S. Pat. No. 6,141,096 discloses such an optical biomolecular detection method involving labeling sample DNAs with fluorescent dye, reacting the sample DNAs with probes immobilized on a chip, and detecting the samples DNAs which are fluorescently labeled and bound to the surface of the chip using a confocal microscope or CCD camera. However, it is difficult to apply the optical detection method to micro-sized chips.
U.S. Pat. Nos. 6,096,273 and 6,090,933 disclose electrochemical methods for detecting DNA hybridization using metallic compounds that are susceptible to oxidation and reduction. The metallic compounds form metal-DNA complexes through hybridization, and the metal-DNA complexes are electrochemically detected (Anal. Chem., Vol. 70, pp. 4670–4677, 1998; J. Am. Chem. Soc., Vol. 119, pp. 9861–9870, 1997; Analytica Chimica Acta, Vol. 286, pp. 219–224, 1994; Bioconjugate Chem., Vol. 8, pp. 906–913, 1997). However, the electrochemical method also inconveniently needs an additional labeling process.
Further, assay methods using no labels such as fluorescent dye have been developed. For example, a method for detecting the binding of biomolecules by measuring a difference in mass before and after binding using a quartz crystal microbalance is disclosed in Anal. Chem., Vol. 70, pp. 1288–1296, 1998. Assay methods involving matrix assisted laser desorption/ionization (MALDI) mass spectrometry are disclosed in Anal. Chem., Vol. 69, pp. 4540–4546, 1997 and U.S. Pat. No. 6,043,031.
Micromechanical methods capable of detecting even a single base mismatch are disclosed in Science, Vol. 288, pp. 316–318, 2000 and Proc. Natl. Acad. Sci. USA, 98, 1560, 2001, which use a microfabricated cantilever as a mechanical sensor for detecting the molecular binding force before and after binding of DNA probes and target molecules. However, the method needs an expensive separate laser device in order to precisely measure the deflection of cantilever beams.
Therefore, there is a need to develop a method for sensitively and efficiently detecting the binding of biomolecules directly as an electrical signal without using expensive additional devices, such as a laser device.